Antennas used in analyzing electromagnetic radiation emissions and immunity of various devices should have relatively broad band or so-called frequency independent operating capability. Moreover, it is desirable to minimize the physical size of such an antenna for portability as well as cost considerations. For a considerable portion of the frequency band used in the above-mentioned electromagnetic compatibility testing, as well as in some communication applications, a half wave length dipole antenna is physically too large for many operating environments. In this regard, physical size restraints often require the use of so-called electrically small antennas or antennas that resonate at a resonance frequency corresponding to about 0.1 wave length of the emitted or received signal. Impedance matching or providing some form of radiating element shaping or loading, or both, can produce a dipole type antenna that will resonate at a frequency lower than that determined by its dimensions relative to the half wave length resonance frequency of conventional dipole antennas.
A popular form of shaped element dipole antenna is the so-called opposed triangular outline wire or "bowtie" antenna. The triangular outline wire antenna is an approximation to the infinite planar sheet triangular element antenna, which is substantially frequency independent. A conventional planar triangular outline wire bowtie antenna resonates at a frequency where its length is about 0.32 wavelength of the emitted or sensed radiation. However, in the above-referenced electromagnetic compatibility testing application, as well as in certain communications applications, it has been considered desirable to decrease the resonance frequency further so that the antenna may be operated to emit or sense radiation at low antenna loss factors and greater signal resolution and strength in lower frequency ranges. In particular, it has been considered desirable in the application of electromagnetic compatibility test antennas to provide suitable antenna operation at radiation frequencies below 200 megahertz and particularly down to frequencies as low as 20 megahertz. It is to these ends that the present invention has been developed with a view to providing a shaped element dipole antenna with a lower resonance frequency and, in combination with other antenna arrays, such as log periodic dipole antenna arrays, for use at signal frequencies below the resonance frequency. In such circumstances, any improvement in antenna gain is welcome.